Anticipated Alternative Instrument-Rate Paths in Policy Simulations

This paper specifies how to do policy simulations with alternative instrument-rate paths in DSGE models such as Ramses, the Riksbank’s main model for policy analysis and forecasting. The new element is that these alternative instrument-rate paths are anticipated by the private sector. Such simulations correspond to situations where the Riksbank transparently announces that it plans to implement a particular instrument-rate path and where this announcement is believed by the private sector. Previous methods have instead implemented alternative instrument-rate paths by adding unanticipated shocks to an instrument rule, as in the method of modest interventions by Leeper and Zha (2003). This corresponds to a very different situation where the Riksbank would nontransparently and secretly plan to implement deviations from an announced instrument rule. Such deviations are in practical simulations normally both serially correlated and large, which seems inconsistent with the assumption that they would remain unanticipated by the private sector. Simulations with anticipated instrument-rate paths seem more relevant for the transparent flexible inflation targeting that the Riksbank conducts. We provide an algorithm for the computation of policy simulations with arbitrary restrictions on nominal and real instrument-rate paths for an arbitrary number of periods after which a given policy rule, including targeting rules and explicit, implicit, or forecast-based instrument rules is implemented. When inflation projections are sufficiently sensitive to the real interest-rate path, restrictions on real interest-rate paths provide more intuitive and robust results, whereas restrictions on nominal interest-rate path may provide somewhat counter-intuitive results.